Basics of a Good Rural Road!

Transcription

1 Basics of a Good Rural Road! WTA Convention -- October 27, 2015! By Steve Pudloski! Transportation Information Center thanks its partners for their support and assistance

2 Three sessions this morning! 8:30!Characteristics of!!!!a Well Built Road!!!9:30!Break!!9:45!Traffic Safety and!!!!traffic Engineering!!10:45 Break!!11:00!Road Maintenance!!!!and Operations!!Noon Lunch!

3 Session 3: Road Maintenance and Operations! WTA Convention! on October 27, 2015! Transportation Information Center thanks its partners for their support and assistance

4 Session 3 Topics Speed Management Pavement Management PASER / WISLR Road Maintenance

5 WHAT WE KNOW ABOUT SPEED, SPEEDING, SPEED LIMITS AND SAFETY

6

7 Some facts about speed Speeding reduces a drivers ability to steer safely around curves and objects in the road. Speeding increases the distance required to stop in emergencies Crash severity increases with the speed of the vehicle at impact. The effectiveness of restraint devices decline as impact speed increases.

8 Some facts about speed Chance of death, disfigurement, or debilitating injury grows with higher speeds at impact. They double for every 10 mph over 50 mph. In a crash the vehicle changes speed rapidly, but the occupants keep moving until they hit something or are restrained. When speeding there is a greater chance that other drivers will misjudge how fast you are going.

9 Why Set Speed Limits? Inability of some drivers to judge the capabilities of their vehicle Different risk choices for drivers. They may not consider other drivers Some drivers underestimate or misjudge the effects of speed on crash probability and severity. They don t know the danger! (public education)

10 Benefits of Speed Limits Reduce dispersion in speeds (Called speed variance or differential) Reduce potential for vehicle conflicts and severity of those conflicts Attempt to balance risk (safety) and travel time (mobility)

11 What We Know about Speed, Speed Limits, and Safety Motorists perceptions of safe and comfortable govern their speeds Personal characteristics Age, Vehicle characteristics Size, Roadway characteristics Design speed, Environmental conditions Weather, How do we know this? RESEARCH

12 What We Know about Speed, Speed Limits, and Safety Effects of Raising and Lowering Speed Limits (Research by M.R. Parker, FHWA, 22 states, 1997) Drivers select speeds irrespective of posted speed limits Lowering posted speed limit did not lower vehicle speeds Raising posted speed limit did not raise vehicle speeds Drivers do not routinely drive 5 to 10 mph above the posted speed limit

13 What We Know about Speed, Speed Limits, and Safety Assessment of Speed Zoning Criteria (Research for FHWA, 50 sites, 1990) In no case was compliance good - 70% of all drivers were speeding The 85% speed averaged about 10 mph over posted speed limits Most posted limits were below the 50% speed and average speed There is little consistency in setting speed limits across and within the states.

14 What We Know about Speed, Speed Limits, and Safety High speeds lead to more severe crash outcomes, changing limits from 55 mph to 65 mph resulted in 22% increase in fatalities (16 states, TRB, 1990) Speed kills pedestrians -- the fatality rate of a pedestrian hit by vehicle at 20 mph is 5 Percent at 40 mph is 80 Percent

15 What We Know about Speed, Speed Limits, and Safety Safety and the 85% speed (Kessler, U of Illinois, 1959; Cirillo, FHWA, 1968; Solomon, FHWA, 1974) Overwhelming majority of drivers believe that the 85% speed feels safe Reduced speed variance leads to a reduced crash risk Conclusions: speed and speed zoning?

16 Crash Rate and Deviation from Average Speed

17 85% Speed, Crash Rate, and Deviation from Average Speed

18 Conclusions (Philosophy) about Speed and Setting Speed Limits Use prevailing speed to set speed zones (the speed most drivers freely choose) Named the 85% speed, at which 85% of freely flowing traffic travels at or below Speed limits should be set a little below design speed (no more than 10 mph) Design speeds may be hazardous to pedestrians and bicyclists change the design speed or provide alternate facility

19 What is a Pavement Management System (PMS)?! A set of tools that can help decision makers find cost-effective strategies for providing, evaluating, and maintaining pavements in a serviceable condition.!!!!fhwa definition!